CN116507442A - Method for processing material - Google Patents

Abstract

The invention relates to a method for processing a material (2) by means of a pulsed laser (1), wherein a sequence (S) of laser pulses (10) is introduced into the material (2) for processing, wherein the sequence (S) of laser pulses (10) is composed of at least two Sequence Elements (SE), wherein one Sequence Element (SE) comprises a single laser pulse (10), a specific series of single laser pulses (10) or a group of laser pulses (10), preferably GHz laser pulse groups, and each Sequence Element (SE) is assigned specific sequence element characteristics, which comprise the position of the laser focus of the sequence element, and the position of the laser focus of each Sequence Element (SE) of the sequence (S) is adjusted in a sequence element-accurate manner in a plane perpendicular to the propagation direction of the laser pulse, and/or the position of the laser focus of each Sequence Element (SE) of the sequence (S) is adjusted in a sequence element-accurate manner along the propagation direction of the laser pulse.

Description

Method for processing material

Technical Field

The invention relates to a method for processing materials by means of laser pulses of a pulsed laser, in particular by means of laser pulses of an ultrashort pulsed laser, wherein the processing can be performed using high laser power.

Background

In ablation and separation methods based on the introduction of ultra-short laser pulses, high demands are often placed on the geometry of the kerf or trench and the quality of the cutting edge. While high process throughput should be achieved.

To meet these requirements, in conventional ablation and separation methods, a focused laser beam is directed onto the workpiece along a processing trajectory. Here, energy is typically deposited in the material at constant time intervals (e.g., synchronized with the repetition rate of the laser) at different positions determined by the feed. To optimize these conventional ablation and separation methods, the processing characteristics of the focused laser beam can be modified by beam shaping and thus, for example, a specially shaped cutting edge (with, for example, a large cutting edge steepness) is obtained.

Spatial optimization of acousto-optic deflectors for energy deposition is proposed, as disclosed for example in US 9036247 B2, US 9776277B2, US 10391585 B2.

Disclosure of Invention

Based on the known prior art, it is an object of the present invention to provide an improved method for processing materials and a corresponding device.

This object is achieved by a method for processing a material having the features of claim 1. Advantageous developments can be gathered from the dependent claims, the description and the figures.

Accordingly, a method for processing a material by means of a pulsed laser is proposed, wherein laser pulse sequences are introduced into the material for processing, wherein the beginning of each sequence is synchronized with the fundamental frequency of the laser, wherein the laser pulse sequences consist of at least two different sequence elements that are spatially and temporally offset from one another, wherein the sequence elements comprise individual laser pulses, or groups of laser pulses, preferably groups of GHz laser pulses, and wherein each sequence element is assigned specific sequence element characteristics. In this case, the sequence element characteristics include the position of the laser focus of the sequence element, and the position of the laser focus of each sequence element of the sequence is adjusted in a sequence element accurate manner.

Here, the material to be processed may be a material such as a metal foil, a polymer, or a plastic. The material to be processed may also be a semiconductor, for example an elemental semiconductor such as silicon or germanium, or a group III-V semiconductor such as gallium arsenide, or an organic semiconductor, or any other type of semiconductor. For example, the material may be a silicon wafer. In particular, the material may be a layer system, wherein each layer can be selected from the group of metals, polymers, plastics or semiconductors.

In this case, the laser provides laser pulses of a laser beam, wherein each individual laser pulse forms a laser beam in the direction of beam propagation. In particular, the laser may be an ultra short pulse laser, wherein the pulse length of each individual laser pulse is preferably shorter than 10ns, preferably shorter than 500ps.

Instead of a single laser pulse, the laser may also provide groups of laser pulses, wherein each group of pulses comprises the emission of a plurality of laser pulses. In this case, the laser pulses may be emitted very densely back and forth over a specific time interval, ranging from a few picoseconds to a few nanoseconds. In particular, the laser pulse bursts may be GHz pulse bursts, wherein the series of successive laser pulses of the respective pulse burst occur in the GHz range.

A laser pulse is introduced into the material, as a result of which the material can be processed. In this case, introducing may mean that the energy of the laser beam is at least partially absorbed within the material. The focal point of the laser beam can be located above or below the surface of the material to be processed in the volume of the material to be processed in the direction of propagation of the beam. The focal position can also be precisely located on the surface of the material to be processed.

In particular, the term "focusing" can generally be understood as a targeted intensity increase, wherein the laser energy is concentrated in a "focal region". In particular, in the following, the expression "focusing" is therefore used independently of the actually used beam shape and the method used to cause the intensity boost. The location of the intensity increase along the direction of beam propagation may also be affected by "focusing". For example, the intensity boost may be nearly punctiform and the focal region may have a gaussian intensity cross section, as provided by a gaussian laser beam. The intensity boost may also be constituted linearly, with a Bessel-type focal region occurring around the focal position, as may be provided by a non-diffracted beam. In addition, other more complex beam shapes are possible, the focal positions of which extend in three dimensions, such as a multi-point profile consisting of a gaussian laser beam and/or a non-gaussian intensity distribution.

Due to the absorption of energy from the laser beam, the material heats up according to the intensity distribution of the laser and/or transitions to a temporary plasma state due to electromagnetic interactions between the laser and the material. In particular, it is thus possible to use not only linear absorption processes but also nonlinear absorption processes, which are achieved by using high laser energy or laser intensity. Accordingly, the material is modified, in particular at the focal point of the laser, since the intensity of the laser beam is greatest there. This is achieved in particular in that a part of the material can be separated from the material compound, for example melted or evaporated. Thus, with regard to the interaction between the laser and the material to be processed, processing processes known per se, which are known, for example, as laser drilling, percussion drilling or laser ablation, can be used.

It is also possible to apply or introduce material modifications in or on the material due to the interaction of the laser with the material to be processed.

Material modification is understood to mean a permanent change in the thermal equilibrium of the material to be processed, for example a network of the material or a (local) density of the material, which modification is causally derived from local heating by incident direct laser radiation, and subsequent cooling and/or electron relaxation processes.

The material modification in or on the material may be, for example, a modification of the structure of the material (in particular, a crystalline structure, and/or an amorphous structure, and/or a chemical structure, and/or a mechanical structure).

If introduced primarily into the volume of the material, the material modification is located within the material. In contrast, if a material modification primarily modifies the surface of a material, the material modification is located on the material. However, in particular, the material modification may be introduced into or applied to the material depending on the focal position and beam profile of the laser beam.

The material modification may also be a direct change in physical properties (e.g., strength, and/or flexural strength, and/or resistance of the material to bending and shear forces, as well as shear and tensile stresses). In particular, the material modification may also be a local change in density, which may depend on the material selected. For example, density variations in the material may cause stress and compression regions that are harder than untreated material. Furthermore, two adjacent materials can be connected to each other by material modification, in particular welding.

According to the method presented here, a sequence of laser pulses is introduced into the material for processing the material, wherein a sequence is composed of at least two different sequence elements. The sequence elements may include a single laser pulse, a specific series of single laser pulses, or a laser pulse burst, wherein the pulse burst can also be a GHz laser pulse burst. It is also possible to combine individual laser pulses and/or single pulse trains and/or pulse groups in a sequence element. The laser pulses of the individual sequence elements are first provided by a pulsed laser.

Each sequence element is assigned a specific sequence element characteristic. In this case, the sequence element characteristics include, for example, characteristics determined by a pulsed laser, such as wavelength or pulse duration. However, the sequence element characteristics may also include characteristics not determined by the pulsed laser itself, but imparted by other methods or means.

In this case, the sequence element characteristics include the position of the laser focus of each sequence element, wherein the position of the laser focus of each sequence element is adjusted in a sequence element accurate manner. In particular, this may mean that the position of the laser focus is adjusted in a serial element-accurate manner in a plane perpendicular to the propagation direction of the laser pulse and/or that the position of the laser focus is adjusted in a serial element-accurate manner along the propagation direction, so that the laser focus can be freely positioned within the accessible positioning volume.

The laser beam can be focused in the propagation direction by means of corresponding optical elements. During focusing, the intensity of the laser beam is maximized toward the location of the laser focus. Accordingly, the laser beam intensity upstream or downstream of the laser focal position in the beam propagation direction is lower than that at the laser focal position itself. This applies in particular to gaussian beams which allow a defined focusing to be achieved. In the case of an approximately non-diffracted beam, such as in a bessel beam or an experimental implementation thereof, there is no or little focusing and thus an extended focal range rather than a defined focal position tends to occur in the direction of beam propagation.

By shifting the position of the focal point of the laser in the direction of propagation of the beam, the penetration depth of the laser with respect to the surface of the material to be processed can thus be determined, wherein the penetration depth is given by the distance of the focal point position from the surface of the material.

By means of corresponding optical elements, it is also possible to position the laser beam, for example, in a plane perpendicular to the direction of propagation of the beam. For example, tilting the optical unit may allow the laser beam to be positioned at a different location than the original location obtained by the non-tilting optical unit.

For example, the laser beam can also be deflected accordingly by means of an acousto-optic deflector unit or scanning unit (for example a galvanometer scanner), so that in this way a corresponding positioning of the laser beam perpendicular to the direction of propagation of the laser beam can be achieved on the material to be processed. By shifting the position of the laser focus in a plane perpendicular to the direction of propagation of the beam, an adjustment of the position in a two-dimensional plane can thus be achieved to accommodate the processing of the material.

The adjustment of the position of the laser focus in a plane perpendicular to the direction of propagation of the beam may be limited to a working area having a size of, for example, between 10 and 100 focus diameters. By limiting the working area a very fast and accurate positioning can be achieved. Such a fast and accurate positioning of the laser beam on the material to be processed can be achieved, for example, by using an acousto-optic deflector unit.

Thus, the exact position at which the material is processed is determined by the sequence element characteristics for each of the at least two sequence elements. Thus, the laser pulses may be introduced into the material to be processed at least two different positions in one sequence.

Accordingly, the sequence can form a so-called multi-segment tool by means of different focal positions of the individual sequence elements, which forms a corresponding form or shape that can be used for processing the material, similar to a punch with predefined processing positions that are fixedly arranged relative to one another. Accordingly, the multi-segment tool provides a predetermined machining geometry that is comprised of at least two sequence elements at least two different locations. Thus, a predetermined machining geometry can be machined during one sequence and the same position can be machined with the same sequence element characteristics throughout the multiple sequences.

Accordingly, the laser pulse sequence in this case comprises a specific series of defined sequence elements, wherein the entire sequence forms a multi-segment tool. In principle, sequence elements are already different if they differ from each other in terms of one of their sequence element properties.

For example, a sequence may include three sequence elements. In this case, the first sequence element may comprise a single laser pulse, wherein the sequence element characteristics of the first sequence element, for example, predetermine that the single laser pulse is precisely focused on the surface of the material to be processed. The second sequence element may comprise a GHz laser pulse train, wherein the sequence element characteristics of the second sequence element, for example, predetermine that the focal position of the GHz laser pulse train should be located below the surface of the material to be processed. For example, the third sequence element may comprise a specific series of laser pulses, in particular a time-specific series of laser pulses, similar to a morse code, i.e. for example the third sequence element may be constituted by a series of pulses of different lengths. For example, the sequence element characteristics of the third sequence element predetermine that the focal position of the particular series should be above the surface of the material to be processed.

For example, in the case of transparent materials, it is also possible to use a multi-segment tool to create material modifications by means of non-diffracted light beams, which then in a second step cause separation of the materials or cause welding of different materials. However, multi-segment tools may also cause a change in a physical property of the material, such as writing a nanograting in the material by changing the refractive index of the material.

Sequence element characteristics may also include polarization. In this case, polarization describes the orientation, in particular the orientation of the electric field vector of the laser beam with respect to the spatial or temporal variation of the propagation direction of the laser beam. For example, the sequence element may have a sequence element characteristic of s-polarization or p-polarization or circular polarization or elliptical polarization.

The sequence element characteristics can be adjusted in a precise manner for the sequence element. This means that two directly successive sequence elements can be different and that a corresponding adjustment of the sequence element characteristics can be made precisely for each sequence element. In other words, there is no overlap between two different sequence elements when adjusting the sequence element characteristics.

In particular, a first sequence element may have a first focus position and an immediately following second sequence element may have a second focus position. In particular, this applies even if the sequence element comprises more than one laser pulse in a particular series of laser pulses.

Thus, by adapting the sequence element characteristics to the desired process parameters in a manner that is accurate to the sequence element, for example, at the full repetition rate of a pulsed laser, an ablation instrument can be composed of a plurality of laser pulses, by means of which the spatial energy introduction can be optimally adapted to the respectively provided processing process.

Another advantage is that the pulse energy requirement can be reduced compared to pure beam shaping, since the corresponding beam shape or its effect can be reshaped or simulated by a highly dynamic, precise shift of the focal position during processing to the sequence element.

Furthermore, the sequence element characteristics may also include pulse energy and/or intensity, and the pulse energy and/or intensity may be adjusted in a sequence element accurate manner for all sequence elements.

If the sequence element is a single laser pulse, the pulse energy is the energy transmitted by the single laser pulse. The intensity is produced by the quotient of the transmitted laser energy and the size of the region in which the laser experiences an increase in intensity.

If the sequence element is a particular series of individual laser pulses, the pulse energies may be added together in their entirety over the particular series of individual laser pulses. A particular series, for example consisting of six individual laser pulses and having a total of 6 microjoules of pulse energy, correspondingly comprises 6 individual laser pulses, for example having an individual energy of 1 microjoule. Thus, the pulse energy may be defined as if the sequence element were a single laser pulse.

If the sequence element is a GHz laser pulse train, the pulse energy may be the energy transmitted through the entire GHz laser pulse train.

The pulse energy, that is to say one of the sequence element characteristics, can be adjusted for each sequence element in a sequence element-accurate manner, which means that successive sequence elements can have different energies. For example, the first sequence element may be a single laser pulse that transmits 1 μj of energy. The subsequent second sequence element may be, for example, a 1GHz laser pulse train, which is composed of a plurality of laser pulses and transmits 2 μj of energy as a whole. The same applies to laser pulses of a specific series of pulses.

In particular, the sequence element characteristics may have a combination of pulse energy and focus position. For example, the first sequence element may be a single laser pulse having the characteristic of a sequence element transmitting 1 μj of energy and in this case the focal position is located on the surface of the material to be processed. The second sequence element may be a 1GHz laser pulse burst having the characteristic of a sequence element transmitting 5 muj of energy and in this case the focal position is located in the volume of material to be processed.

As a result, the laser pulse energy can be coupled to the position of the laser focus. Thus, any intensity profile may be introduced into the material, for example, to create different ablation openings and cross-sections.

The sequence element characteristics may also include temporal development of the sequence element during its introduction.

This may mean that the pulse profile of the sequence element varies with time. For example, in the case of a single pulse, this may mean that the edge steepness of the laser pulse is adjustable, that is to say that the so-called rise time and decay time of the pulse are adjustable. For example, rectangular or triangular pulses or saw-tooth pulses can thus be realized, or in particular more complex pulse shapes, which can also have modified pulse durations. For example, it can thus be used to determine the amplitude of successive laser pulses in a particular series or GHz laser pulse train of laser pulses.

Preferably, the sequence element characteristics may comprise a time interval between one sequence element and a preceding and/or following sequence element, and the time interval may be adjusted for each sequence element of the sequence, preferably given by the fundamental frequency of the laser, a minimum time interval and/or a temporal interval variation.

The time interval, i.e. the further sequence element characteristic of the sequence element, is determined from the start of the first sequence element to the start of the further sequence element.

For example, the time interval between the first sequence element and the second sequence element may be 100ns and the time interval between the second sequence element and the third sequence element may be 150ns.

The time interval relative to the previous and/or subsequent sequence elements is measured. This may mean that the second sequence elements are determined with respect to the time positioning of the first sequence elements. The time interval may also be determined with respect to the third sequence element. For example, one sequence may have a first sequence element and a third sequence element, wherein the second sequence element can be located between the first sequence element and the third sequence element. If the time interval between the first sequence element and the third sequence element has been determined, the descriptions of the time interval between the first sequence element and the second sequence element or between the second sequence element and the third sequence element are equivalent to each other.

The time interval of the sequence elements can be adjusted in a precise manner for the sequence elements. In particular, this means that the time interval between sequence elements in a sequence may differ between different sequence elements. Where the sequence element is a particular series of individual laser pulses, the adjustment made in a precise manner of the sequence element may mean that each individual laser pulse has a precisely specific time interval relative to the preceding or following laser pulse.

Accordingly, an ablation instrument may be composed of a plurality of sequence elements, wherein energy deposition within the ablation instrument is not performed simultaneously, but rather is modulated precisely in time for optimal spatial energy deposition.

For example, the time interval between sequence elements may also be zero, so that the laser pulses of the sequence elements are introduced into the material simultaneously. For example, only the position of the laser focus may differ between two sequence elements, such that the two sequence elements are introduced into the material synchronously.

In this case, the minimum time interval between the sequence elements is given by the fundamental frequency of the pulsed laser (the so-called seed frequency). In this case, the seed frequency is the natural repetition rate of the laser, which corresponds to the undisturbed repetition rate of the laser. Typically, the seed frequency is significantly greater than the spacing between sequence elements.

Preferably, the sequence element characteristics further comprise a beam geometry which is adjusted in a sequence element-specific manner for each sequence element, wherein the laser beam formed by the laser pulses of the sequence element is preferably divided into at least two sub-laser beams, wherein the sub-laser beams are particularly preferably introduced into the material synchronously with one another and/or the sub-laser beams are particularly preferably imaged side by side and spaced apart from one another along a line.

The beam geometry (i.e. the further sequence element characteristic) in this case comprises, for example, the spatial configuration of the intensity distribution of the laser beam.

In particular, the beam geometry includes a beam profile, such as a gaussian beam profile or a non-gaussian beam profile. For example, the beam profile may also be elliptical or triangular or linear or have any other shape.

However, the beam geometry also includes sub-laser beams generated by a single laser beam and their spacing from each other. Since the laser beam is preferably divided into at least two sub-laser beams, the number of laser beams that can be simultaneously used for processing the material is doubled or multiplied as long as the laser energy of each sub-laser beam is sufficiently high. The beam geometry comprising a plurality of laser foci is also referred to as a multipoint geometry.

The sub-laser beams are preferably introduced into the material simultaneously. This may mean that the sequence element characteristics of the sub-laser beams are identical except for the position of the laser focus. In particular, the two sub-laser beams have the same size with respect to the time interval of the preceding or following sequence element. Furthermore, simultaneous introduction means that two sub-laser beams impinge on the material simultaneously.

The sub-laser beams may be introduced into the material side by side with each other. In particular, this means that these sub-laser beams do not overlap. In case of more than two sub-laser beams, this may mean that all sub-laser beams lie in one line, in particular in one straight line.

The precise adjustment of the beam geometry in a sequence element means that the sequence element characteristics can vary from sequence element to sequence element and, for example, from one single pulse to another. In particular, this means that the first sequence element has a first beam geometry and the second sequence element has a second beam geometry.

Thus, it is possible to alternate between the different sequence elements between a multi-point energy distribution, a line energy distribution, and a single focal point energy distribution, for example, to simultaneously deposit a portion of the energy within the ablation instrument in the material and to process other regions at defined time intervals.

Also, the heat build-up within the ablation instrument can thereby be additionally optimized. By synchronous positioning of the individual laser pulses of the sub-laser beams, the temporal distance of successive sequence elements can be maximized to minimize the introduction of heat from the laser into the material.

By combining various sequence element characteristics, a specific ablation instrument or laser pulse sequence may be provided by means of which a material ablation or separation process may be achieved.

In particular, the creation of various ablation tools will allow the ablation of shaped laser beams to be mimicked, wherein these individual sequence elements are not equal to the laser beam to be mimicked. The effect of the beam profile of the desired processing beam can thus also be shaped by a corresponding distribution of the sequence elements.

Preferably, the sequence element characteristics are adjusted in a pulse-accurate manner for each sequence element, wherein the adjustment of the sequence element characteristics is preferably synchronized with the fundamental frequency of the laser.

This means that the respective sequence element characteristics are predetermined in a defined manner for each laser pulse and that in particular no different sequence element characteristics are assigned to one laser pulse.

The sequence, in particular the beginning of the sequence, may be synchronized with the fundamental frequency of the pulsed laser.

In this case, the fundamental frequency of the pulsed laser and in particular the seed frequency is used in the overall system for synchronization within the sequence. For example, the seed frequency is used to actuate a fast switch (e.g., an acousto-optic deflector) and thus to determine the position of the laser focus. However, the seed frequency is also used to generate the time interval between sequence elements. Thus, precise tuning of the various controllable optical elements based on the seed frequency allows for more precise control of the process.

If GHz laser pulse bursts are used, the start of the laser pulse bursts is, for example, synchronized with the seed frequency.

Preferably, at least two sequences of laser pulses are introduced into the material for processing the material, wherein preferably the same sequence elements of each sequence are introduced into the material at the same location.

It is thus achieved that the ablation instrument provided by the different sequence elements acts on one location of the material to be processed a plurality of times and that, for example, different locations combined in the ablation instrument are sequentially loaded a plurality of times with laser energy.

In this case, the sequence may comprise between 2 and 10000 sequence elements, typically 25 sequence elements.

This allows for the creation of complex ablation tools or sequences by which material can be processed very precisely.

It can then be achieved that the ablation geometry provided by the individual segments is reliably operated when this sequence is operated a plurality of times, and can be expanded in terms of the energy input.

The wavelength of the laser pulses may be between 200nm and 2500nm and/or the pulse duration may be shorter than the repetition duration of the laser pulses, in particular between 500ps and 10fs, typically between 20ps and 100 fs.

It may be particularly advantageous that the repetition rate of the laser is in the range of the switching time of a fast switch (e.g. an acousto-optic deflector) and that the pulse duration of the laser beam is significantly shorter than these orders of magnitude, e.g. ps/fs pulses. This allows the acousto-optic deflector to deflect each laser pulse of the laser individually.

Furthermore, this method can be used particularly advantageously for UV wavelengths, since due to the high repetition rate, multiple pulses can be used here effectively for shaping the combined beam.

Preferably, one sequence may be specific to one processing stage of the material, and the first sequence may be introduced into the material along a processing path during the first processing stage, and the second sequence may be introduced into the material along the same processing path during the second processing stage, wherein the first sequence is different from the second sequence.

Specific to each processing stage may mean that each processing stage of the material is assigned a specific laser sequence. For example, the first processing stage may involve a pre-processing, or post-processing or main processing of the material, such as a separation process or a cutting process.

In particular, the laser pulse sequence may be varied between processing stages. Here, there is no need to remove material from the device and reposition it. Instead, it is sufficient to merely change the laser pulse sequence so that different processing steps can be performed step by step without having to reposition the material between different workstations.

In particular, this allows multiple processing of the same location of the material and the conventional processing phases are reproduced accordingly.

The ablation instrument can thus be guided over the workpiece and, if necessary, switched at different process stages or for different geometries. This allows a high average laser power to be optimally achieved.

Further preferably, between the first sequence and the second sequence, the spatial arrangement of the sequence elements in the processing plane can be rotated about an axis parallel to the propagation direction of the laser beam. Accordingly, if a non-point focus (i.e., a spatially extended focus) is used, the machining plane becomes a machining volume accordingly. This is understood to be encompassed by the term "processing plane".

For example, this may mean that during a first process stage the spatial geometry of the ablation instrument corresponds to a certain first shape and during a second process stage the geometry corresponds to a second shape, wherein the first shape and the second shape transition into each other by rotation. In particular, such rotation is performed around the propagation direction of the laser light, such that the rotation produces the same effect as the rotation of the laser beam or ablation instrument relative to the material to be processed.

In particular, this may mean: rotation corresponds to reordering of the individual focus positions, as no component or module is physically rotated. In particular, the reordering of sequence elements may correspond to tool changes.

Such tool changes may be implemented for relatively complex geometries or more complex ablation procedures that pass through the workpiece multiple times, wherein the temporal and spatial positioning of individual pulses within the ablation tool is altered by switching in the control device.

In a further preferred configuration, a sequence may comprise a plurality of processing stages and preferably comprises roughing, smoothing and polishing, wherein the sequence elements arranged first in space in the feed direction in the processing plane correspond to the first processing stage, the sequence elements arranged subsequently correspond to the second processing stage, and the sequence elements arranged last correspond to the last processing stage. In other words, different processing phases can be formed successively in the feed direction through the material to be processed using the same ablation tool.

By time varying the characteristics of individual sequence elements, multiple process steps, such as roughing, smoothing and polishing, can be achieved within a single ablation instrument (i.e., within a sequence).

For example, the preceding high energy and large area laser pulses may represent a rough machining process. For example, a subsequent laser pulse with a smaller focus and more moderate energy may represent a smoothing process. For example, the surface modification may be introduced at the end by GHz laser pulse bursts, which may correspond to a polishing process.

For example, a forward position of the laser focus in the feed direction may cause material ablation, while a rearward position of the laser focus may smooth the cutting edge, and another more rearward position of the laser focus may clean the smoothed edge.

As a result, the material can be subjected to different processing stages without, for example, changing work stations.

The machining process may be an ablation process and the size of the ablation opening and the cross-sectional profile of the ablation opening may be determined by a sequence of laser pulses.

During ablation, laser energy of the sequence elements is at least partially deposited in the material, causing the material to heat up and/or the material to evaporate and be ablated according to the energy distribution deposited in the material.

The energy distribution deposited in the material is given by a sequence of laser pulses, in particular the focal position and the laser energy predetermine the final energy distribution. In particular, the shape of the ablation may thus be determined by a series of sequence elements and different ablation tools or ablation geometries may be achieved by a single system without having to perform physical tool changes.

In this case, the ablation opening is an opening in the surface of the material during ablation. The cross-sectional profile is the cross-section in which the direction of propagation of the light beam is and extends at least partially through the volume of material.

For example, the ablation opening may be circular and the cross-sectional profile may be triangular, such that the ablation portion is generally conical. For example, the ablation opening may also be square and the cross-sectional profile may be triangular, such that the ablation portion is generally pyramidal. For example, the ablation opening may be circular and may be rectangular in cross-section, such that the ablation portion is generally cylindrical.

The laser beam and the material may be displaced relative to each other by the feed.

By means of the feed movement, the laser beam can be guided over the material or the material can be guided under the laser beam.

In particular, the feeding motion and the introduction of the sequence or ablation instrument may occur in parallel. In addition to the corresponding sequence element characteristics, focal position, the feed motion along any feed trajectory must also be taken into account in order to precisely determine the position of incidence of the laser light on the material.

Due to the described combination of spatial and temporal aspects, it is possible to guide the ablation instrument over the workpiece and to adapt it precisely to the ablation procedure, depending on the geometry to be processed.

The duration of the laser pulse train may be less than the requirements for successive laser pulses during processing, which are determined by the amount of feed between the material and the laser pulse train

The spatial representation of the ablation instrument or sequence is given by the different focal positions of the sequence elements in the sequence.

In particular, a feed is also understood as a superimposed movement for positioning a sequence element, wherein if the sequence takes into account a superimposed feed, the local geometry of the tool can be adapted to the feed.

The laser pulses of the laser pulse train can be introduced into the material in a delay-compensated manner.

The delay compensation compensates for movement of the laser pulse along the laser beam prior to incidence on the material and relative movement between the laser pulse and the material during flight due to the feed movement. In particular, deflection movements which may occur due to changes in the beam geometry are also considered. In particular, the compensation can take place in real time.

This ensures that the laser pulses are introduced at the set incidence point, thereby improving the quality of the material processing.

The above object is also achieved by means of a device for processing materials having the features of claim 14. Advantageous developments of the device can be gathered from the dependent claims, the description and the figures.

Accordingly, a device for processing a material by means of laser pulses of a pulse laser is proposed, wherein successive pulses are introduced into the material spatially and temporally offset from one another, comprising a control device, preferably an FPGA ("field programmable gate array= Field Programmable Gate Array") or an ASIC ("application specific integrated circuit= Application Specific Integrated Circuit"), wherein at least one laser pulse sequence is stored in a memory of the control device, which sequence comprises not only sequence elements but also sequence element characteristics, wherein the control device is connected in communication with the pulse laser and the deflection system, and the control device controls the pulse laser and the deflection system or transmits control instructions to the pulse laser and the deflection system.

Furthermore, the control device may also be connected to the feeding device to compensate for positional deviations or to ensure a positional accurate tool change.

Furthermore, a deflection system, in particular an acousto-optic deflector unit, adapted for the laser energy may be provided, which deflection system is capable of causing deflection of the laser beam and/or dividing the laser beam into a plurality of sub-laser beams, and which deflection system may comprise a filtering system for filtering a specific spatial frequency.

Preferably, an imaging system is provided to image the laser pulses into a processing plane, which is preferably arranged in or on the surface of the material.

Furthermore, a feeding device, in particular a scanner, preferably a galvanometer scanner, may be provided for moving the laser beam in the processing plane.

In order to achieve a corresponding procedure using an ablation instrument or sequence, the sequence element characteristics must be adjusted with the sequence element. In particular, it is necessary to change the pulse position rapidly within a small working field, for example on the time scale of the seed frequency. This requires a controller that is synchronized with the laser seed frequency and that enables actuation.

Typically, the respective control means is based on an FPGA (field programmable gate array) with a fast linked memory, wherein a plurality of sequence element characteristics, such as focal position, pulse energy or pattern (single pulse or laser pulse burst) can be stored for each sequence element of the ablation instrument or sequence. Furthermore, the control device is connected to the pulsed laser system and the deflection system.

In this case, the control instructions or their execution in all connected devices are synchronized with the seed frequency of the laser, so that a common time base exists for all components. Due to the correspondingly fast actuation of the pulsed laser and the deflection system, a plurality of sequence element characteristics can be set and altered with the sequence elements. This relates, for example, to the pulse energy and also to the position of the laser focus on the workpiece.

The control of the position in a pulse-accurate manner is typically achieved by means of an acousto-optic deflector unit. In an acousto-optic deflector unit, an acoustic wave is generated in an optically adjacent material by an alternating voltage on a piezoelectric crystal, which acoustic wave periodically modulates the refractive index of the material. The wave may propagate through the optical material, for example, as a propagating wave or as a wave packet or as a standing wave. Here, due to the periodic modulation of the refractive index, a diffraction grating for the incident laser beam is realized. The incident laser beam is diffracted at the diffraction grating and is thus at least partially deflected at an angle to its original beam propagation direction. The grating constant of the diffraction grating and thus the deflection angle in this case depend inter alia on the wavelength of the sound wave and thus on the frequency of the applied alternating voltage. For example, a deflection in the x-direction and in the y-direction can thus be produced by a combination of two acousto-optic deflectors in a deflector unit.

For example, the imaging system may be a lens system, in particular a fourier optical unit. For example, the fourier optical unit may be a so-called 4f optical unit, whereby the focal position of the deflection system output may be imaged onto or into a processing plane in the material. For example, the 4f optical unit is constituted by two members, and an image side focal point of the first member in the beam propagation direction coincides with an object side focal point of the second member. This may allow imaging the object-side focus of the first component and the image-side focus of the second lens into the processing plane.

In this case, a component may in particular be an optical component having imaging properties, for example having a focusing or collimating effect. Among others, this is: imaging or curved mirrors, beam shaping elements, diffractive optical elements, lenses such as converging or diverging lenses, fresnel zone plates, and other free-form components.

In the ideal mathematical case, the focal plane and the corresponding plane are planes oriented perpendicular to the direction of propagation of the light beam and are in particular not curved and have only a two-dimensional extent. However, in practical implementations, the optical components cause minor curvature and deformation of these planes, and thus these planes are typically at least partially curved. If the focal point as described above is not punctiform, the focal point has a spatial extent, and thus the focal plane becomes a focal volume in which the imaging of the laser beam is still sufficiently clear, as described below.

The focal plane is therefore always referred to below, however the available focal volume is always also considered, even if this is not explicitly mentioned. Furthermore, the explanations given above also relate to the machining plane used hereinafter.

In particular, positioning tolerances are obtained for the position of the components used. For example, the positioning tolerance may be up to 20%, preferably 10%, so that a component that is e.g. 10cm from the reference point still enables a sufficiently clear image even at 9cm and 11 cm. Accordingly, if the components are all positioned within positioning tolerances, the imaging is automatically sufficiently clear. Furthermore, two planes or two points "coincide" means that the associated volumes at least partially overlap.

In particular, this also allows an object-side intermediate plane of the imaging system, in which for example a spatial frequency filtering can take place, to be imaged onto the workpiece. Thus, the machining plane in the material can be reached by an intervention in the object-side intermediate plane of the imaging optical unit and the beam shape can be adjusted in the machining plane.

The imaging system may provide an optical intermediate plane, such as an output of an acousto-optic deflector unit or an intermediate filter optical unit for the imaging system. The object side midplane is then imaged onto a workpiece or material. Here, the expansion or contraction of the ablation instrument may also be performed by the imaging system.

Furthermore, the material can be moved by the feeding device, in parallel with which a spatial representation of the ablation instrument (that is to say the focal position of the individual sequence elements) is produced by the acousto-optic deflector unit. Instead of or in addition to the feeding device, a conventional scanner (e.g. a galvanometer scanner) may be superimposed on the deflection system. Both the feed device and the scanner optical unit can be synchronized by the seed frequency, so that there is a common time base for feed, beam deflection, beam shaping and pulsed laser driving.

In particular, various position data of the feeding device or signals corresponding thereto (e.g. the deflection angle of a galvanometer scanner) can also be fed back to the control device in order to calculate and apply the delay compensation of the tool.

More complex spatial composition of the ablation instrument, such as a multi-point geometry, a line, may be achieved by the deflection system, but may also be achieved by shifting the focal position along the direction of beam propagation, or aberration correction of a single focal point (which occurs by passing through various optical elements).

It is also conceivable to use EOD systems, MEMS, TAG optical units, liquid crystal systems (such as spatial light modulators) and CBC systems, as well as diffractive optical elements or combinations thereof for generating complex beam geometries, provided that the performance and switching speed appear to be favourable for the respective application.

Drawings

Preferred further embodiments of the present invention are explained in more detail by the following description of the drawings, in which:

FIGS. 1A, 1B show schematic representations of a method according to the prior art;

fig. 2A, 2B, 2C show schematic representations of the proposed method;

fig. 3A, 3B show another schematic representation of the proposed method;

FIG. 4 shows a schematic representation of the time dependence in an ablation instrument or in a sequence;

FIGS. 5A, 5B show schematic representations of a rotated ablation instrument;

fig. 6 shows a schematic representation of an apparatus for carrying out the method; and

fig. 7A, 7B, 7C show schematic representations of the optical path of an apparatus for carrying out the method.

Detailed Description

The preferred embodiments are described below with reference to the accompanying drawings. In this case, the same reference numerals are provided to the same, similar or identically functioning elements in different drawings, and duplicate descriptions of these elements are partially omitted to avoid redundancy.

Fig. 1A schematically illustrates a method for processing a material according to the prior art. A pulsed laser is used to provide laser pulses 10 which are focused on the material 2 to be processed so as to be partially absorbed therein, so that a portion of the material is heated and eventually ablated (or removed).

The pulse laser usually predefines the pulse length TP, the time interval TA between laser pulses (which is also given by the repetition rate of the laser), and the energy E carried by the laser pulses. In this respect, the pulse laser predefines a sequence S of laser pulses, wherein each individual laser pulse is a single sequence element, to which the laser 1 inherently imparts pulse length, pulse energy and distance to the following pulse. After introducing a sequence S consisting of a single laser pulse into the material 2, the sequence S is repeated again. In other words, all pulses of the sequence and their sequence element characteristics are identical.

During the time that the pulsed laser provides the laser pulse 10, the material is moved relative to the laser beam with a feed V. Thus, each laser pulse 10 introduced into the material has a spatial offset Δy, such that the laser energy is deposited at different workpiece locations. Thereby, an ablation or cutting procedure may be performed.

Fig. 1B shows the various incidence positions of the laser pulse 10 from fig. 1A on the material 2. By means of the relative feed motion V, the laser pulse 10 is introduced into the material 2 along a straight line. The position of incidence between each pulse is shifted by Δy=vta.

In this method, therefore, the spatial position of the laser focus on the material 2 is determined only by the feed motion V, and the temporal energy input is determined by the fixed setting of the pulsed laser.

Fig. 2A schematically illustrates the method presented herein. In this case, the processing of the material takes place by means of a sequence S consisting of laser pulses. The laser pulse sequence S is formed by at least two sequence elements SE, which in turn are each formed by a laser pulse, a specific series of individual laser pulses or a laser pulse group or a laser pulse train. For each sequence element, the position of the laser focus is adjusted in a sequence element accurate manner. Thus, at least two different positions of the laser focus are provided in one sequence.

A sequence S can thus form so-called ablation tools by means of different positions of the laser focus of the individual sequence elements, which ablation tools form a corresponding form or shape which is almost as shaped as a punch with predefined machining positions which are fixedly arranged opposite one another.

In this case, the position of the laser focus is adjusted as a sequence element characteristic in a sequence element-accurate manner, wherein the adjustment takes place in a plane perpendicular to the propagation direction of the laser beam. The shapes of the laser focus positions "1" to "6" depicted in fig. 2A are shown in cross section with respect to the beam propagation direction of the laser beam. To some extent, fig. 2A shows the incidence position of a single laser pulse after running a complete sequence without material displacement.

Thus, the sequence S or ablation instrument may be composed of a plurality of sequence elements SE, wherein the energy deposition within the ablation instrument need not be simultaneous, but can be precisely adjusted in time.

Fig. 2B shows the temporal configuration of a sequence S and fig. 2C shows the ablation cross-sectional geometry of the sequence S produced in the material 2.

For example, the first sequence element SE1 is in this case a single laser pulse 10, which is output into the material at the focal position "1" at the beginning of the sequence S. This is followed by a time interval TA before the second sequence element SE 2. For example, the second sequence element SE2 is also a single laser pulse 10, wherein the laser beam formed by the second laser pulse 10 is split into two different sub-laser beams, for example by a deflection system or a beam splitter optical unit. Thus, the second sequence element SE2 has a different beam geometry than the first sequence element SE 1. The laser pulse 10, which is divided into two sub-laser beams, is correspondingly synchronously introduced into the material at positions "2" and "3".

This is followed by a time interval TA before the third sequence element SE 3. The third sequence element SE3 is a single laser pulse 10, wherein the laser beam formed by the third laser pulse is again divided into two different sub-laser beams. Thus, the third sequence element SE3 has a different beam geometry than the first sequence element SE1 and the second sequence element SE 2. Laser pulses 10 are synchronously introduced into material 2 at positions "4" and "5". This is followed by a time interval TA before the fourth sequence element SE 4. In this case, the fourth sequence element SE4 is schematically provided as a GHz laser pulse group 14, which is then introduced into the material 2 at position "6".

Due to the partly simultaneous introduction of these sub-laser beams, the heat accumulation caused by the ablation instrument may be optimized, as the time interval between successive pulses may be maximized due to the simultaneous introduction. Heat accumulation is reduced as the material has more time to cool between pulses.

In another configuration, the opposite effect, i.e. a targeted and rapid heating of a predetermined expansion area of the material, can also be achieved by introducing sub-laser beams.

The shape of the ablation instrument and the shape of the energy distribution actually introduced into the material may be different, depending on the amount of feed and the time interval between the sequence elements. In general, deformation of the ablation instrument during the procedure may be avoided by feeding with so-called delay compensation, as follows.

During the procedure, the ablation instrument of fig. 2A produces a specifically shaped ablation section with ablation opening 24 and cross section 22. Such a section 22 is shown, for example, in fig. 2C. The ablation opening 24 has a large diameter 28 at the surface of the material, wherein the diameter 28 tapers as the depth 26 of the material increases.

The shape of the cross-section 22 of the ablation section is understood by the various focal positions in fig. 2A where energy is introduced into the material. The diameter 28 of the ablation opening 24 is determined by the spatial distance between the focal positions "2" and "3". In contrast, in the center of the ablation section, material 2 is ablated at focal positions "1", "4", "5" and "6", so that the energy density deposited there is significantly greater. The result is that the ablation in this area is significantly deeper.

Thus, the ablation instrument may achieve a precise ablation procedure due to the combination of the spatially and temporally sequential element characteristics depicted in fig. 2A and 2B.

Fig. 3A shows another configuration of the proposed method. A sequence consisting of sequence elements SE is introduced into the material 2 within a certain period of time TS. In this case, a certain time may be mainly determined for introducing energy into the material during the time period TS, but the time period TS may also have phases in which energy may not be introduced into the material. In particular, the phase during which no energy is introduced into the material is decisively determined by the determined time interval between the last sequence element SE and the next sequence element SE or the first sequence element SE1 of the repeated sequence S.

Fig. 3B shows another ablation instrument in which the laser focus position of sequence element SE of sequence S is adjusted in a pulse-accurate manner. The ablation instrument has different focal positions in a plane perpendicular to the direction of beam propagation, but the ablation instrument also has a focal position that is shifted along the direction of beam propagation, i.e., position "1". As a result, the focal diameter in the machining plane appears to be larger, but the intensity of the focal position is smaller.

Furthermore, fig. 3B shows how the ablation instrument is displaced relative to the material surface, generally by the feed V. Different tools are also available depending on the order of the sequence elements.

If the feed V during time TS is significantly less than the spatial extent of the ablation instrument, the distribution of energy deposited in material 2 may correspond to the distribution of the ablation instrument. At high feed rates, deformation of the ablation instrument may be avoided by delay compensation.

Fig. 4 shows a possible pulse composition of another ablation instrument. In this case, a plurality of laser pulses 10 or sequence elements SE having different pulse energies or time intervals or sequence element characteristics are combined. For example, a sequence may include between 2 and 10000 sequence elements. In this case, the individual pulse duration is in the picosecond or femtosecond range, in particular between 500ps and 10fs, typically between 20ps and 100fs, with the wavelength of the laser pulses being between 200nm and 2500 nm.

The sequence defining the ablation instrument first includes a first sequence element SE1 (which is a single laser pulse 10), followed by a second sequence element SE2 (which is a particular series of laser pulses 10), followed by a third sequence element SE3 (which is a GHz laser pulse cluster 14), followed by a fourth sequence element SE4 (which is also a particular series of laser pulses).

In this case, all sequence elements of the sequence start in synchronization with the seed frequency of the laser. In particular, it is not mandatory that each sequence element end up synchronized with the seed frequency of the laser. This can be seen in particular in sequence element SE3, in which the end of the energy introduced by the GHz laser pulse train lies between the clock pulses of the seed frequency.

The sequence element SE1 consists of only a single laser pulse. The energy of the laser pulse, the time interval relative to the latter sequence element and possibly the beam geometry are determined by the sequence element characteristics.

The second sequence element includes a specific series of laser pulses (e.g., three laser pulses). In the case of the second sequence element, the pulse energy of the laser pulse is reduced stepwise in the sequence element. In principle, the laser pulses of a particular series of laser pulses can be understood as individual sequence elements and assigned their own sequence element characteristics. However, by grouping such sequence elements, a particular energy introduction form can be fixedly defined and reused. The last pulse of the sequence element is followed by a time interval to the next sequence element that is significantly longer than the interval between pulses within the sequence element.

The third sequence element SE3 is a GHz laser pulse group, which is finally followed by a fourth sequence element SE4, which is composed of a specific series of further laser pulses, in which the laser energy is increased stepwise.

In addition to the temporal order of the sequence elements, each sequence element can also be assigned a beam geometry, for example in such a way that the beam profiles of the individual sequence elements are all different. In particular, all sequence elements can be adjusted in a sequence element accurate manner, so that each sequence element of the sequence can be assigned an individual sequence element characteristic.

Fig. 5 illustrates, in an exemplary manner, tool replacement of an ablation tool. The ablation instrument is comprised of a total of ten different laser focal positions disposed within a triangle. During tool change, the positioning in time and space of individual sequence elements within the ablation instrument is changed by switching the manipulation. For example, switching of the steering may include rotating the ablation instrument generally about the direction of beam propagation by a suitable optical unit.

For example, rotation of the ablation instrument is one possibility to change the spatial arrangement of the focal position. Here, in fig. 5B, the ablation instrument of fig. 5A is rotated about the direction of beam propagation by an angle. For example, when the laser beam 12 is not deflected from its beam propagation direction, the focal position "1" is achieved. Thus, rotation is performed around this focal position "1".

As can be seen from fig. 5A, the focus positions "2" and "3" are arranged at the same Y height with respect to the focus position "1". For example, when the laser beam 12 is divided into sub-beams accordingly, the energy of the laser pulses may be synchronously introduced to the focal positions "2" and "3".

In fig. 5B, the energy of the laser pulse is still introduced into focus positions "2" and "3" simultaneously, but the ablation instrument is rotated about focus position "1" such that the laser pulse energy is introduced into focus position "2" spatially before focus position "3". Thereby, a temperature gradient, for example, with a specific ablation function or processing function can be formed.

However, such rotation is typically applied in superposition with the feed in order to direct the energy deposition along a complex trajectory on the material.

In particular, it can be seen that the position of the laser focus is effectively reordered by rotation of the ablation instrument. In fact, no optical unit or optical module is rotated during apparent rotation, and deflection and beam shaping are adjusted only in accordance with rotation.

Fig. 6 shows a schematic structure of a device 8 for processing materials, which device is capable of carrying out the above-described processing method. The control means 4, for example an FPGA, comprise or can be connected to a memory 40, on which the sequence S with the sequence elements SE and the sequence element characteristics are stored. Distributed memory systems are also possible, wherein preferably fast-connected internal memory and slow-connected RAM modules in an FPGA can cooperate.

The advantage of the memory 40 is that various multi-segment tools or sequences can be stored in the control device 4, so that in case of successive processing of the material 2 with different process steps, a fast switching between different processes is possible.

The control device 4 is connected in communication with the pulsed laser 1 and can thus access, for example, the seed frequency of the laser. Since the control device 4 is communicatively connected to the pulsed laser 1, it is also possible that the control device 4 can transmit laser-specific sequence element characteristics to the pulsed laser 1 and control the pulse release. These laser-specific sequence element characteristics are, for example, pulse energy or pulse spacing or operating modes, such as the single-pulse or GHz laser pulse burst-operating mode of the laser.

In addition to the pulsed laser 1, a control device 4 is connected in communication with the deflection system 3. The deflection system 3 is responsible for deflecting the laser beam 12 or dividing the laser beam 12 into a plurality of sub-beams. However, the deflection system may also achieve beam splitting and/or shaping and/or longitudinal focus shifting and/or lateral positioning of the laser beam and for this purpose optionally cooperate with the imaging system 5. The deflection system 3 is synchronized with the pulse laser 1 via the control device 4 such that each laser pulse 10 of the pulse laser 1 is assigned a separate focal position by the deflection system 3. The connection of the pulsed laser 1 to the deflection system 3 and the control device 4 thus enables the pulse-accurate and thus sequence-element-accurate control of the sequence element SE or the sequence element characteristic.

The focal position provided by the deflection system 3 is imaged by the imaging system 5 into a processing plane 20 of the material 2. For example, the imaging system 5 may be a lens system. However, the imaging system 5 may also contain a filter element. The sequence element SE provided by the pulsed laser 1 and processed by the deflection system 3 is then introduced into the processing plane 20 of the material 2 and causes processing there, wherein the sequence element has sequence element properties that are precisely adjusted for the sequence element.

During the provision of the laser pulses 10 by the pulsed laser 1, the material 2 may be moved with respect to the one or more laser beams 12 with a feed V. For this purpose, a feed device 6 is provided, which is integrated into the imaging system 5, for example in the form of a scanning optical unit. In particular, the feeding device may be configured for delay compensation and may be connected to the control device for this purpose.

Fig. 7A schematically shows a portion of a device 8 for ablating material 2. In this case, the pulsed laser 1 provides a laser beam 12 in which the laser pulse 10 of the laser 1 propagates.

In the embodiment shown, the laser beam 12 is typically directed through a deflection system 3, for example an acousto-optic deflector unit. The laser beam 12 is focused by means of adjacent lenses and is then optionally guided through the filter element 7, where the beam profile of the laser beam 12 can be manipulated and optimized for the machining process. In particular, this makes it possible to filter out the spatial frequencies, so that the laser pulses 10 imaged onto the material 2 have a high contrast.

Finally, the image of the filter element 7 is imaged by the imaging system 5 onto or into the material 2. This may be achieved, for example, in that the imaging system is, for example, a fourier optical unit. Thus, in general, in this case, the ablation instrument is created by the combination of the deflection system 3 and the filter element 7.

In this case, the filter element 7 is located upstream of the first lens 50 in the beam direction by a distance corresponding to the focal length F1 of the first lens. The second lens 52 is located downstream of the first lens 50 in the beam direction. The image-side focal point of the first lens 50 and the object-side focal point of the second lens 52 are located between the first lens 50 and the second lens 52. The two foci coincide such that the spacing of the two lenses 50, 52 corresponds to the sum of the focal lengths f1+f2. A working plane 20 in or on the material 2 is located downstream of the second lens 52. The machining plane 20 is arranged at a distance F2 from the lens 52, said distance corresponding to the focal length of the second lens 52.

The ablation instrument is imaged into the treatment plane 20 by an imaging system. In this case, imaging can also be achieved in a reduced manner, for example by a factor of between 2 and 500, in particular by a factor of 25. By shrinking, in particular, smaller scale ablations can be achieved.

The laser pulse 10 of the laser beam 1 is incident into the material in the processing plane and is at least partially absorbed by the material 2. Thereby, the material 2 may be heated and/or changed to a temporary plasma state, thereby partly evaporating the material and thus ablating the material. During this process, the ablation instrument may be moved relative to the material 2 by the feeding device 7.

As shown in fig. 7B, instead of moving the workpiece 2 by the feeding device 6, or in addition to the feeding device 6, a scanner (e.g., a galvanometer scanner 62) may be used between the lenses 50, 52 of the imaging system 5. Due to the fast reaction time of the galvo scanner 62, a particularly accurate machining process can be performed. In particular, position and/or angle information about the galvo scanner 62 and/or the feeding device 6 can be recorded at a high measurement rate by means of a corresponding encoder and can be transmitted to the control device at high speed and can be used for performing delay compensation by means of the deflection system 3 and for checking the tool composition.

Fig. 7C shows another embodiment in which the deflection system 3 is focused directly onto the material 2 by means of a lens 52. For example, the deflection system 3 may be a microelectromechanical system (MEMS). Thus, if filtering and a scanner are not required, installation space can be saved to achieve a compact device.

All the individual features presented in the embodiments can be combined with each other and/or interchanged within the scope of the invention without departing from the scope of the invention.

List of reference numerals

1. Pulse laser

10. Laser pulse

12. Laser beam

120. Sub-laser beam

122. Sub-laser beam

14. Laser pulse group

16. Fundamental frequency

2. Material

20. Plane of working

22. Cross section of

24. Ablation opening

26. Ablation depth

28. Diameter of

3. Deflection yoke

4. Control device

40. Memory device

5. Imaging system

50. First lens

52. Second lens

6. Feeding device

62. Galvanometer scanner

7. Filter element

8. Device and method for controlling the same

TP pulse length

Time interval between TA laser pulses

T time

Energy of E laser pulse

S sequence

SE sequence elements.

Claims (15)

1. A method for processing a material (2) by means of a pulsed laser (1), wherein a sequence (S) of laser pulses (10) is introduced into the material (2) for processing the material (2) to be processed,

wherein the start of each sequence (S) is synchronized with the fundamental frequency (16) of the laser (1),

wherein the sequence (S) of laser pulses (10) is formed by at least two different Sequence Elements (SE) which are spatially and temporally offset from each other,

wherein the Sequence Element (SE) comprises a single laser pulse (10), a specific series of single laser pulses (10), or a group of laser pulses (10), preferably GHz laser pulses, wherein,

Each Sequence Element (SE) is given a specific sequence element characteristic, and

the sequence element characteristics include the position of the laser focus of the sequence element, an

The position of the laser focus of each Sequence Element (SE) of the sequence (S) is adjusted in a sequence element accurate manner.

2. Method according to claim 1, characterized in that the sequence element characteristics comprise pulse energy and/or intensity, and that the pulse energy and/or intensity of each Sequence Element (SE) of the sequence (S) is adjusted in a sequence element-accurate manner.

3. A method according to any one of claims 1 or 2, characterized in that the sequence element characteristics comprise a temporal development of the sequence element during its introduction.

4. Method according to any of the preceding claims, characterized in that the sequence element characteristics comprise a time interval between a Sequence Element (SE) and a preceding and/or following Sequence Element (SE) and that this time interval is adjusted for each Sequence Element (SE) of the sequence (S), wherein preferably a minimum time interval and/or time interval variation is given by the fundamental frequency (16) of the laser (1).

5. The method according to any of the preceding claims, characterized in that the sequence element characteristics comprise a beam geometry and that the beam geometry is adjusted in a sequence element-accurate manner for each Sequence Element (SE), wherein preferably the laser beam (12) formed by the laser pulses (10) of the Sequence Element (SE) is divided into at least two sub-laser beams (120, 122), wherein the sub-laser beams (120, 122) are particularly preferably introduced into the material (2) synchronously with each other and/or the sub-laser beams (120, 122) are particularly preferably imaged side by side and spaced apart from each other along a line.

6. The method according to any of the preceding claims, characterized in that the sequence element characteristics are adjusted in a pulse-accurate manner for each Sequence Element (SE), wherein the adjustment of the sequence element characteristics is preferably synchronized with the fundamental frequency (16) of the laser (1).

7. Method according to any of the preceding claims, characterized in that at least two sequences (S) of laser pulses (10) are introduced into the material (2) for processing the material (2), wherein preferably the same Sequence Elements (SE) of each sequence (S) are introduced into the material (2) at the same location.

8. The method according to any of the preceding claims, characterized in that,

-the wavelength of the laser pulses is between 200nm and 2500nm, and/or

The pulse duration is smaller than the repetition duration of the laser pulses, in particular between 500ps and 10fs, typically between 20ps and 100 fs.

9. Method according to any one of the preceding claims, characterized in that each sequence (S) comprises between 2 and 10000 Sequence Elements (SE), preferably 25 Sequence Elements (SE).

10. Method according to any of the preceding claims, characterized in that one sequence (S) is specific to one processing stage of the material (2) and that a first sequence (S) is introduced into the material (2) along a processing path during a first processing stage and a second sequence (S) is introduced into the material (2) along the same processing path during a second processing stage, wherein the first sequence (S) is different from the second sequence (S).

11. Method according to claim 10, characterized in that the spatial arrangement of the Sequence Elements (SE) in the machining plane (20) is rotated between the first sequence (S) and the second sequence (S) about an axis parallel to the propagation direction of the laser beam (12).

12. Method according to any one of the preceding claims, characterized in that one sequence (S) comprises a plurality of processing phases, preferably roughing, smoothing and polishing, wherein the Sequence Elements (SE) arranged first in the feed direction spatially in the processing plane (20) correspond to the first processing phase, the Sequence Elements (SE) arranged subsequently correspond to the second processing phase, and the Sequence Elements (SE) arranged last correspond to the last processing phase.

13. Method according to any one of the preceding claims, characterized in that a sequence (S) of laser pulses (10) is introduced into the material (2) in a delay-compensated manner.

14. Device (8) for processing a material (2) by means of laser pulses (10) of a pulsed laser (1), wherein successive laser pulses (10) are introduced into the material (2) to be processed spatially and temporally offset from one another, comprising:

a control device (4), preferably an FPGA, wherein at least one sequence (S) is stored in a memory (40) of the control device (4), which sequence comprises not only Sequence Elements (SE) but also sequence element characteristics of each Sequence Element (SE), wherein,

The control device (4) is connected in communication with the pulsed laser (1) and with the deflection system (3), and

the control device (4) is designed and configured to control the pulsed laser (1) and the deflection system (3) or to transmit control instructions to the pulsed laser (1) and the deflection system (3).

15. The device (8) according to claim 14, characterized in that,

the deflection system (3) comprises an acousto-optic deflector unit and/or

The deflection system (3) is capable of causing a spatial deflection of the laser beam (12) and/or dividing the laser beam (12) into a plurality of sub-laser beams (120, 122), and/or

The deflection system comprises a filter system (7) for filtering the spatial frequencies, and/or

Comprising an imaging system (5) for imaging the laser pulses (10) into a processing plane (20) of a material (2) to be processed, and/or

Comprising a feed device (6), preferably a scanner, particularly preferably a galvanometer scanner (62), for moving the laser beam (12) in a processing plane (20) of the material (2) to be processed.